The present invention relates generally to the design and construction of seal systems useful in a gas turbine engine. More particularly, the present invention has one application with a carbon seal system having a rotating seal runner with a flow channel for uniformly distributing cooling fluid. Although the invention was developed for use in a gas turbine engine, certain applications may be outside of this field.
It is well known that a gas turbine engine integrates a compressor and a turbine that have components that rotate at extremely high speeds relative to each other, and across which there are pressure differentials that make the provision of seals for minimizing fluid leakage very important. Prior designers of seal systems have generally used a sealing device consisting of a plurality of arcuate carbon material segments arranged to form a stationary carbon ring that forms a rubbing interface with a rotating seal runner.
The rubbing interface between the rotating seal runner and the carbon ring minimizes or prevents the leakage of fluid through the seal, however if the heat generated by the rubbing interface is not adequately dissipated the resulting fluid leakage at the seal interface may become excessive. A failure to control the temperature of the rotating seal runner can result in thermal distortion of the seal runner and a corresponding degradation of the seal's performance that is manifested by an excessive fluid leakage.
A carbon seal system requires the precise geometric fit between the stationary carbon ring and the rotating seal runner to assure that an intimate rubbing interface is obtained between the mating components. The rubbing interface between the mating components is critical to the performance of the seal, and certain tolerances associated with the seal components are measured in millionth of an inch. In order to maintain the precision geometric fit between the mating components of the rubbing interface, prior designers of carbon seal systems have typically utilized a fluid cooling medium to extract excessive heat from the seal runner.
The conventional technique utilized to minimize the overheating of the seal interface includes the delivery of a cooling fluid onto the underside of the rotating seal runner. One approach to delivering the cooling fluid onto the underside of the rotating seal runner is to spray the cooling fluid from a stationary nozzle that is positioned proximate the seal runner. The relative motion between the rotating seal runner and the stationary nozzle causes a uniform film of cooling fluid to be deposited on the seal runner that results in a uniform extraction of thermal energy from the runner. Stationary nozzles provide a consistently even film of cooling fluid on the underside of the rotating seal runner, however their applicability on many gas turbine engines is limited by physical constraints that prevent the nozzle from being located proximate the seal runner.
A second approach to delivering the cooling fluid utilizes a rotating distributor to deliver the cooling fluid onto the underside of the rotating seal runner. The rotating distributor is typically affixed to the seal runner, and a steady stream of cooling fluid is delivered through a central passageway in the rotating distributor to the underside of the seal runner. A series of openings in the rotating distributor dispense the cooling fluid onto the seal runner. Inherently, because of the absence of relative motion between the distributor and the seal runner there is an inevitable uneven distribution of cooling fluid on the underside of the seal runner. Prior designs have utilized a greater quantity of openings formed at one end of the central passageway in order to produce a more even distribution of cooling fluid on the underside of the rotating seal runner.
It is generally well known that a carbon seal system having a rotating distributor must include a large quantity of openings in order to deliver an even film of cooling fluid on the underside of the seal runner. If this design parameter is not satisfied, an uneven film of cooling fluid is distributed across the seal runner, which causes an uneven extraction of heat.
This uneven extraction of heat can lead to the warping and deformation of the seal runner that will result in gaps between the seal runner and the carbon sealing element. Any voids, openings, or gaps in the rubbing interface of the seal system will cause excessive fluid leakage through the seal. A carbon seal system design having a large quantity of cooling fluid dispensing openings can be utilized, however as the quantity of openings increase there arises significant complexity in interconnecting the components. Manufacturing concerns will serve to limit the quantity of cooling fluid dispensing openings that can be utilized, this in turn will effect the evenness of the distribution of cooling fluid on the seal runner and the associated heat transfer therefrom.
Even with a variety of early designs there remains a need for an improved sealing system. The present invention satisfies this need in a novel and unobvious way.